Technologies for producing ethanol or the like have been commercialized that involve converting woody biomass or other biomass into sugars with dilute sulfuric acid or concentrated sulfuric acid, and then subjecting them to solid-liquid separation, neutralizing the liquid phase thereof, and utilizing the resultant components as biomass materials for ethanol fermentation or the like (Patent Documents 1 and 2). Further, by using sugar as starting material, production of chemical industrial raw material (e.g., lactic fermentation) has been considered. Biomass as used herein refers to a living organism integrated in material circulation in the global biosphere or accumulation of organic materials derived from living organisms (see JIS K 3600 1258).
Sugarcane, corn, and other materials, currently used as alcohol raw materials, have been originally used for food. Using such food resources as long-term stable industrial resources is not preferable in view of life cycle of valuable food.
For this reason, it is a challenge to efficiently use cellulose resources such as herbaceous biomass and woody biomass, which are considered as potentially useful resources.
Cellulose resources include cellulose ranging from 38% to 50%, hemicelluloses components ranging from 23% to 32%, and lignin components, which are not used as fermentation materials, ranging from 15% to 22%. Due to many challenges, the industrial studies have been conducted targeting certain fixed materials, and no technologies have been disclosed yet on production systems taking into account diversity of the materials.
Production systems targeting fixed materials see almost no point regarding countermeasures for waste problems and global warming, because those systems have attempted such countermeasures with a method that brings more disadvantages to fermentation materials than starch materials. Thus, there has been a need for a method applicable to a variety of wastes in broader sense. Enzymatic saccharification methods are also considered as a future challenge due to its low efficiency. Acid treatment only achieves a low saccharification rate of about 75% (a basis for components that can be saccharified), due to excessive decomposition of sugar. Thus, the ethanol yield achieves only 25% by weight of cellulose resources (Non-Patent Document 1 and Patent Document 3).
[Patent Document 1] Japanese Patent Application Laid-open No. 9-507386
[Patent Document 2] Japanese Patent Application Laid-open No. 11-506934
[Patent Document 3] Japanese Patent Application Laid-open No. 2005-168335
[Non-Patent Document 1] Nikkei Biotechnology & Business, p. 52, September 2002
[Non-Patent Document 2] Biomass-Extensive Use of Bioresources, edited by Japanese Society for Bioscience, Biotechnology, and Agrochemistry, Asakura Publishing Co., Ltd., September 1985